Injection Wells In Michigan

As early as the 1930s, oil and gas operators realized that produced brine could be returned to oil and gas reservoirs through injection. Prior to this time, the brine produced from this activity was primarily discharged at the surface into creeks, ditches, and on-site pits. This had a negative impact to groundwater and surface water quality. By the late 1960’s most of these types of discharges were eliminated. Injection wells became the preferred liquid waste disposal method. Modern injection well requirements date back to 1974 with the passage of the Safe Drinking Water Act (SDWA). By 1980, Underground Injection Control (UIC) regulations were enforced by the US EPA. Since that time there have been significant amendments to the SDWA and UIC rules (on both the federal and state levels) regarding the construction and operation requirements of injection wells to ensure that groundwater, the environment, and public health and safety are protected.

There are over 30 active Class I Waste Disposal Well permits in Michigan and approximately 800 active US EPA Class I Waste Disposal Wells in the United States. Wells of this type are dually permitted by the OGMD and the United States Environmental Protection Agency (US EPA). These wells may be used to dispose either hazardous or non-hazardous wastes. Class I Hazardous Waste Disposal Wells dispose of industrial wastes that meet the hazardous waste criteria as defined within the 1976 Resource Conservation and Recovery Act (RCRA). Michigan currently has 6 Class I Waste Disposal Wells that meet the hazardous waste definition. There are 2 Commercial Class I Hazardous Waste Disposal Wells at one facility which accept waste from other generators and 4 Non-Commercial Hazardous Waste Disposal Wells associated with chemical manufacturing facilities. The remaining active Class I Waste Disposal Wells are utilized for what is considered Non-Hazardous Wastes.

There are approximately 1,100 active Class II injection wells in Michigan and approximately 180,000 active Class II Injection wells in the United States. Except for wells in Indian Country, Michigan has primacy authority delegated for issuance of permits and the enforcement of Underground Injection Control (UIC) requirements for Class II wells. Class II wells are associated with oil and gas exploration and production. In Michigan, about 60% of Class II wells are used for Brine Disposal, with the balance operated as Enhanced Oil Recovery Wells. As the name implies, Brine Disposal wells inject the brine that is produced in conjunction with oil and gas production. This brine is often saltier than seawater and if not handled properly would have the potential to negatively impact the environment and public health. The produced brine is generally considered a waste product. This fluid is disposed into deep confined formations. These formations are far below and isolated from freshwater zones. Enhanced Recovery wells inject fluids into depleted hydrocarbon producing reservoirs. The fluids used in Michigan for this purpose are typically freshwater, brine, and carbon dioxide (CO₂). Depending upon the application, the injected fluids work to increase reservoir pressure, decrease fluid viscosity and displace residual hydrocarbons. The fluids are used to increase production and ultimate recovery of hydrocarbons.

There are over 50 active Class III Solution Mining Well permits in Michigan and approximately 18,500 active Class III Solution Mining wells in the United States. Wells of this type are dually permitted by the OGMD and the US EPA. In Michigan, Class III Solution Mining wells are used to inject fluids (water) into underground salt formations thereby dissolving the salt. The resulting brine is pumped back to the surface where it is evaporated and further processed to obtain the targeted mineral constituents. In Michigan, Solution Mining is mainly used for the generation of food grade salt (NaCl) and Potash (KCl).

There are 17 active Class V Spent Brine Return Flow Well permits in Michigan. These wells are permitted under the Mineral Well Program as a Waste Disposal Well. There are approximately 100 active Class V Spent Brine Return Flow wells in the United States. Wells of this type are dually permitted by the OGMD and the US EPA. In Michigan, these wells are used to dispose of processed brine after the minerals (mainly magnesium compounds) have been extracted. Class V Spent Brine Return Flow wells re-inject this brine into the same formation from which it was withdrawn.

There are currently no Class VI Carbon Sequestration Wells in Michigan and fewer than a dozen in the United States. Wells of this type are dually permitted by the OGMD and the US EPA. Michigan would permit a Carbon Sequestration Well under the Mineral Well program as a Waste Disposal Well. This is an emerging well type in which carbon dioxide (CO₂) is captured and stored underground where it remains geological sequestered permanently. Wells of this type can reduce the amount of greenhouse gas emissions that are added to the atmosphere and would be used by power generation sectors and other industrial sources.

The protection of environment and especially the protection of groundwater and freshwater resources is the primary concern in the site selection, construction, operation, and monitoring of injection wells. This protection is accomplished before the well is drilled by thoroughly reviewing the proposed well design, injection parameters, and the surrounding area, and after the well has been put into use by imposing testing, monitoring, and reporting requirements.

It is essential that injection well proposals are reviewed, designed, and constructed properly. Under no circumstances would an injection well be approved or allowed to operate in Michigan if there are indications that the injected fluids could migrate into freshwater zones. To achieve this goal, the proposed well design, proposed rate of injection, proposed injection pressures, and specific properties of the injected fluid are carefully reviewed to assure compliance with regulations. In addition, an area of review of up to 2 miles is conducted near the injection well proposal. This area of review is done to identify any known geologic features or previously drilled wells that penetrate the proposed injection zone and may pose a risk. It is important that the geologic formations targeted have the ability to accept fluids and that there is proper geologic confinement in the formations above the injection zone. Injection wells are held to a maximum injection pressure to ensure that the geologic formations are not negatively impacted.

In Michigan, there are public noticing requirements for Injection Well permit applications, including a comment period for pending applications. Information related to submitted injection well permit applications in the Oil and Gas program are posted weekly and can be found on the OGMD web page. Information related to submitted injection well permit applications in the Mineral Well program can be found on the OGMD web page. Depending upon the validity of the comments received or issue raised, a public hearing regarding the well may be held. Once all the reviews are complete and the applicant has satisfied the necessary requirements, a permit is issued. At this point the well drilling and construction can begin.

Injection wells are drilled in stages and constructed with multiple steel casing strings (steel pipes) that are cemented in place. The first stage involves drilling the well’s surface casing string. In drilling the surface string, a hole drilled through the freshwater zones and into competent bedrock. By rule this casing must be set at least 100 feet below freshwater, into competent bedrock, and cement is placed on the outside of this casing from the bottom to the top of the hole, thereby sealing the well. The second stage involves drilling a smaller diameter hole below the surface casing. Once the intended depth is reached, another steel casing is installed from the surface and cemented in place. Depending upon the depth of the injection zone, additional drilling, steel casing, and cementing may be used. By rule, a minimum of 250 feet of cement above the injection zone is required around the injection casing. Actual injection is through steel tubing inside the final casing string. The tubing is held in place near the bottom of the well with a special tool called a packer. The packer prevents any fluids from rising back to surface. The area between the tubing and the final casing string is called the annulus. The annulus is filled with a corrosion inhibiting fluid and the pressure within the annulus is monitored to assure that the well maintains integrity.

Figure 1 shows the components and features of a typical Class II Brine Disposal well in Michigan.